Chemical vapor deposition method for depositing a high k dielectric film

ABSTRACT

The invention includes chemical vapor deposition and physical vapor deposition methods of forming high k ABO 3  comprising dielectric layers on a substrate, where “A” is selected from the group consisting of Group IIA and Group IVB elements and mixtures thereof, and where “B” is selected from the group consisting of Group IVA metal elements and mixtures thereof. In one implementation, a plurality of precursors comprising A, B and O are fed to a chemical vapor deposition chamber having a substrate positioned therein under conditions effective to deposit a high k ABO 3  comprising dielectric layer over the substrate. During the feeding, pressure within the chamber is varied effective to produce different concentrations of A at different elevations in the deposited layer and where higher comparative pressure produces greater concentration of B in the deposited layer. In one implementation, a subatmospheric physical vapor deposition method of forming a high k ABO 3  comprising dielectric layer on a substrate includes providing a sputtering target comprising ABO 3  and a substrate to be deposited upon within a physical vapor deposition chamber. A sputtering gas is fed to the chamber under conditions effective to sputter the target and deposit a high k ABO 3  comprising dielectric layer over the substrate. During the feeding, pressure is varied within the chamber effective to produce different concentrations of B at different elevations in the deposited layer and where higher comparative pressure produces greater concentration of B in the deposited layer.

RELATED PATENT DATA

This patent resulted from a continuation application of U.S patentapplication Ser. No. 09/580,733, filed May 26, 2000 abandoned, entitled“Chemical Vapor Deposition Methods and Physical Vapor DepositionMethods”, naming Cern Basceri as inventor, the disclosure of which isincorporated by reference.

TECHNICAL FIELD

This invention relates to chemical and physical vapor deposition methodsof forming high k ABO₃ comprising dielectric layers on a substrate,where “A” is selected from the group consisting of Group IIA and GroupIVB elements and mixtures thereof, and where “B” is selected from thegroup consisting of Group IVA metal elements and mixtures thereof.

BACKGROUND OF THE INVENTION

As DRAMs increase in memory cell density, there is a continuingchallenge to maintain sufficiently high storage capacitance despitedecreasing cell area. Additionally, there is a continuing goal tofurther decrease cell area. One principal way of increasing cellcapacitance is through cell structure techniques. Such techniquesinclude three-dimensional cell capacitors, such as trenched or stackedcapacitors. Yet as feature size continues to become smaller and smaller,development of improved materials for cell dielectrics as well as thecell structure are important. The feature size of 256 Mb DRAMs andbeyond will be on the order of 0.25 micron or less, and conventionaldielectrics such as SiO₂ and Si₃N₄ might not be suitable because ofsmall dielectric constants.

Highly integrated memory devices, such as 256 Mbit DRAMs, are expectedto require a very thin dielectric film for the 3-dimensional capacitorof cylindrically stacked or trench structures. To meet this requirement,the capacitor dielectric film thickness will be below 2.5 nm of SiO₂equivalent thickness.

Insulating inorganic metal oxide materials (such as ferroelectricmaterials, perovskite materials and pentoxides) are commonly referred toas “high k” materials due to their high dielectric constants, which makethem attractive as dielectric materials in capacitors, for example forhigh density DRAMs and non-volatile memories. In the context of thisdocument, “high k” means a material having a dielectric constant of atleast 20. Such materials include tantalum pentoxide, barium strontiumtitanate, strontium titanate, barium titanate, lead zirconium titanateand strontium bismuth tantalate. Using such materials enables thecreation of much smaller and simpler capacitor structures for a givenstored charge requirement, enabling the packing density dictated byfuture circuit design.

One class of high k materials comprises ABO₃, where “A” is selected fromthe group consisting of Group IIA and Group IVB metal elements andmixtures thereof, and where “B” is selected from the group consisting ofGroup IVA elements and mixtures thereof. Such materials can be depositedby chemical or physical vapor deposition methods.

Certain high k dielectric materials have better current leakagecharacteristics in capacitors than other high k dielectric materials. Insome materials, aspects of a high k material which might be modified ortailored to achieve a highest capacitor dielectric constant possiblewill unfortunately also tend to hurt the leakage characteristics (i.e.,increase current leakage). For example, one class of high k capacitordielectric materials includes metal oxides having multiple differentmetals bonded with oxygen, such as the barium strontium titanate, leadzirconium titanate, and strontium bismuth titanate referred to above.For example with respect to barium strontium titanate, it is found thatincreasing titanium concentration as compared to barium and/or strontiumresults in improved leakage characteristics, but decreases thedielectric constant. Accordingly, capacitance can be increased byincreasing the concentration of barium and/or strontium, butunfortunately at the expense of increasing leakage. Further, absence oftitanium in the oxide lattice creates a metal vacancy in such multimetaltitanates which can increase the dielectric constant, but unfortunatelyalso increases the current leakage.

SUMMARY

The invention comprises chemical vapor deposition and physical vapordeposition methods of forming high k ABO₃ comprising dielectric layerson a substrate, where “A” is selected from the group consisting of GroupIIA and Group IVB metal elements and mixtures thereof, and where “B” isselected from the group consisting of Group IVA elements and mixturesthereof. In one implementation, a plurality of precursors comprising A,B and O are fed to a chemical vapor deposition chamber having asubstrate positioned therein under conditions effective to deposit ahigh k ABO₃ comprising dielectric layer over the substrate. During thefeeding, pressure within the chamber is varied effective to producedifferent concentrations of B at different elevations in the depositedlayer and where higher comparative pressure produces greaterconcentration of B in the deposited layer.

In one implementation, a subatmospheric physical vapor deposition methodof forming a high k ABO₃ comprising dielectric layer on a substrateincludes providing a sputtering target comprising ABO₃ and a substrateto be deposited upon within a physical vapor deposition chamber. Asputtering gas is fed to the chamber under conditions effective tosputter the target and deposit a high k ABO₃ comprising dielectric layerover the substrate. During the feeding, pressure is varied within thechamber effective to produce different concentrations of B at differentelevations in the deposited layer and where higher comparative pressureproduces greater concentration of B in the deposited layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is schematic diagram of an exemplary system usable in accordancewith an aspect of the invention.

FIG. 2 a diagrammatic sectional view of a semiconductor wafer fragmentin process in accordance with an aspect of the invention.

FIG. 3 is a diagrammatic sectional view of an alternate embodimentsemiconductor wafer fragment in process in accordance with an aspect ofthe invention.

FIG. 4 is a diagrammatic sectional view of another alternate embodimentsemiconductor wafer fragment in process in accordance with an aspect ofthe invention.

FIG. 5 is a graph representing B concentration as function of thicknessin accordance with an aspect of the invention.

FIG. 6 is a graph representing B concentration as function of thicknessin accordance with an alternate aspect of the invention.

FIG. 7 is schematic diagram of an alternate exemplary system usable inaccordance with an aspect of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

The prior art recognizes the desirability in certain instances offabricating high k dielectric regions of capacitors, such as ABO₃ layersas referred to above, to have variable concentration at differentelevational locations in the thickness of such regions of the “A” and“B” components. For example with respect to titanates, the quantity oftitanium represented by the variable “B” in ABO₃ is impacting relativeto leakage current characteristics and k value in the subject layer.Accordingly in some instances, it might be desirable to fabricate acapacitor dielectric region to have one elevational range of one ABO₃stoichiometry, and another elevational range of the region to have adifferent ABO₃ stoichiometry, utilizing the same or differentcombinations of elements. Further, film morphology and haze can beaffected by the concentration of B in the deposited film. The typicalprior art method of providing variable stoichiometry at selectedlocations throughout the thickness of a high k dielectric region is tovary the precursor flows to the reactor during a chemical vapordeposition which may or may not be plasma enhanced.

For example where higher titanium content is desired, the flow rate ofthe titanium precursor(s) would typically be increased relative to theother precursors. Likewise in this example where less titanium isdesired, the flow rate of the titanium precursor(s) would be reduced toachieve lower titanium content in a desired portion of a depositing highk dielectric region. Unfortunately, changing the precursor flows asdescribed does not typically result in a near instantaneous change intitanium concentration in the deposited layer. Accordingly, there is astabilization problem in varying precursor flows, and a correspondinglag in formation of the selected stoichiometry material.

It has, however, been surprisingly discovered that varying ambientpressure within the chamber during a chemical vapor deposition producesrapid change, stabilization and control in achieving a desiredstoichiometry of a high k ABO₃ comprising dielectric layer on asubstrate. In but one implementation, the invention contemplates achemical vapor deposition method of forming a high k ABO₃ comprisingdielectric layer on a substrate, where “A” is selected from the groupconsisting of Group IIA and Group IVB metal elements and mixturesthereof, and where “B” is selected from the group consisting of GroupIVA elements and mixtures thereof. In the context of this document,Group IIA metal elements consist of Be, Mg, Ca, Sr, Ba, and Ra. GroupIVB metal elements consist of Sn and Pb. Group IVA elements consist ofTi, Zr, Hf and Rf. In accordance with but one aspect of the invention, aplurality of precursors comprising A, B and O are fed to a chemicalvapor deposition chamber having a substrate positioned therein underconditions effective to deposit a high k ABO₃ comprising dielectriclayer over the substrate. During the feeding, pressure is varied withinthe chamber effective to produce different concentrations of B atdifferent elevations in the deposited layer, and where highercomparative pressure produces greater concentration of B in thedeposited layer.

FIG. 1 diagrammatically illustrates but one chemical vapor depositionsystem 10 in accordance with but one implementation of a chemical vapordeposition method in accordance with the invention. Such comprises an Aprecursor feed stream 12 and a B precursor feed stream 14. Such combineand feed to a vaporizer 16. An inert gas stream 18 can be provided alsoto vaporizer 16 to facilitate flow of the vaporized precursors to adownstream chamber.

A chemical vapor deposition chamber 20 is connected downstream ofvaporizer 16. Such includes a showerhead 22 for receiving anddistributing gaseous precursors therein. A suitable wafer holder 24 isreceived within chamber 20. Oxidizer gas feed streams, for example oneor more O₂ and N₂ O streams, are preferably provided upstream of theshowerhead. The deposition is preferably conducted at subatmosphericpressure, with a vacuum pump 26 being diagrammatically illustrated forachieving a desired vacuum pressure within chamber 20. In the mostpreferred implementation, the vacuum pressure during deposition isvaried at least one point during the deposition by manipulating somevacuum pressure control device associated with chamber 20 to producedesired different concentrations of B at different elevations in thedeposited layer. By way of example only, such pressure control devicemight include the illustrated vacuum pressure control valve 28 providedproximate chamber 20. Alternately by way of example only, suchmanipulating might comprise changing upstream ballast flow to vacuumpump 26 downstream of chamber 20, such as represented by arrow 30. For agiven vacuum pump speed, addition of ballast control gas through line 30will decrease the degree of vacuum achieved within chamber 20 forincreasing flows of ballast gas, assuming constant vacuum pump speed.Further by way of example only, such manipulating of a control device tocontrol vacuum pressure within the chamber might comprise changing thespeed of vacuum pump 26. Such manipulation of vacuum pressure byactuating a direct controlling device associated with the chamber ismost preferred in accordance with the invention as enabling rapidcontrol of ambient pressure and changes associated therewith withinchamber 20.

Further most preferably in a process in accordance with but one aspectof the invention, the flows of the precursors are maintainedsubstantially constant while pressure is varied. Even more preferably,with the exception of pressure, all of the conditions of deposition aremaintained substantially constant throughout deposition of the layer onthe substrate. The deposition may or may not be plasma enhanced.

In one example, A in the high k ABO₃ comprising dielectric layerconsists essentially of a mixture of Ba and Sr (i.e., preferably about50%—50%), and B consists essentially of Ti. Example preferred depositionis by metal organic chemical vapor deposition (MOCVD) processes carriergases, with one or more oxidizers being provided within chamber 20 withsuitable MOCVD precursors to deposit a desired barium strontium titanateor other film on a substrate. Example oxidizers include either 100% O₂or a 50—50 mix of O₂ and N₂O. Alternate preferred processing can occurin accordance with my co-pending U.S. patent application Ser. No.09/476,516, filed on Jan. 3, 2000, entitled “Chemical Vapor DepositionMethods Of Forming A High K Dielectric Layer And Methods Of Forming ACapacitor”, listing Cem Basceri as inventor, which is herebyincorporated by reference.

By way of example only, other example preferred high k dielectricmaterials in addition to barium strontium titanate, include

SrTiO₃ ST BaTiO₃ BT Pb(Zr, Ti)O₃ PZT BaZrO₃ BZT

For deposition of BST, example precursors, and by way of example only,include:

Ba(thd)₂ bis(tetramethylheptanedionate) Sr(thd)₂bis(tetramethylheptanedionate) Ti(thd)₂(O-i-Pr)₂(isopropoxide)bis(tetramethylheptanedionate) Ba(thd)₂bis(tetramethylheptanedionate) Sr(thd)₂ bis(tetramethylheptanedionate)Ti(dmae)₄ bis(dimethylaminoethoxide) Ba(methd)₂ bis(methoxyethoxyte,tetramethylheptanedionate) Sr(methd)₂ bis(methoxyethoxyte,tetramethylheptanedionate) Ti(mpd)(thd)₂ bis(methylpentanediol,tetramethylheptanedionate) Ba(dpm)₂ bis(dipivaloylmethanato) Sr(dpm)₂bis(dipivaloylmethanato) TiO(dpm)₂ (titanyl)bis(dipivaloylmethanato)Ba(dpm)₂ bis(dipivaloylmethanato) Sr(dpm)₂ bis(dipivaloylmethanato)Ti(t-BuO)₂(dpm)₂ (t-butoxy)bis(dipivaloylmethanato) Ba(dpm)₂bis(dipivaloylmethanato) Sr(dpm)₂ bis(dipivaloylmethanato)Ti(OCH₃)₂(dpm)₂ (methoxy)bis(dipivaloylmethanato)Adducts (i.e., tetraglyme, trietherdiamine,pentamethyldiethlyenetriamine), solvents (i.e., butylacetate, methanol,tetrahydrofuran), and/or other materials might be utilized with theprecursors.

By way of example only, and where the precursors include metal organicprecursors, example flow rates for the various of such precursorsinclude anywhere from 10 mg/min. to 1000 mg/min. of liquid feed to anysuitable vaporizer. Preferred N₂O flows include from 100 sccm to 4000sccm, more preferably between 500 sccm and 2000 sccm, and mostpreferably between 750 sccm and 1250 sccm. Such flow rates andreduction-to-practice of the invention are with respect to an AppliedMaterials Centura Frame™ processor. A preferred pressure range is from100 mTorr to 20 Torr, with a range of from 1 Torr to 6 Torr being morepreferred. Susceptor temperature is preferably from 100° C. to 700° C.,more preferably from 400° C. to 700° C., with less than or equal to 550°C. being even more preferred and in attaining continuity in thedeposited layer at thicknesses at or below 200 Angstroms, and preferablyat least down to 50 Angstroms. Most preferably, susceptor temperature iskept at less than or equal to 550° C. during all of the deposit to formlayer 16.

The varying of pressure within the chamber during the deposition mightbe conducted in a number of different manners depending upon thefinished composition the fabricator desires. By way of example only,three possible exemplary implementations are described with reference toFIGS. 2-4. FIG. 2 depicts an exemplary substrate 10 comprising a bulkmonocrystalline silicon substrate 12. In the context of this document,the term “semiconductor substrate” or “semiconductive substrate” isdefined to mean any construction comprising semiconductive material,including, but not limited to, bulk semiconductive materials such as asemiconductive wafer (either alone or in assemblies comprising othermaterials thereon), and semiconductive material layers (either alone orin assemblies comprising other materials). The term “substrate” refersto any supporting structure, including, but not limited to, thesemiconductive substrates described above.

An insulative layer 14, such as borophosphosilicate glass (BPSG), isformed over substrate 12. A conductive capacitor electrode layer 16,such as platinum or an alloy thereof by way of example only, is formedover layer 14. A high k ABO₃ comprising dielectric layer 18 is formedthereover in accordance with some aspect of the invention. In thisexemplary depicted example, a plurality of precursors comprising A, Band O are fed to a chemical vapor deposition chamber under some suitablefirst set of conditions effective to deposit a substantially homogenousfirst portion 20 of high k ABO₃ comprising dielectric layer 18. Thefirst conditions in this example are preferably characterized at leastby some substantially constant first pressure.

While feeding the plurality of precursors, the first conditions arechanged to second conditions that at least include a substantiallyconstant second pressure which is different from the first pressureeffective to deposit a substantially homogenous second portion 22 ofhigh k ABO₃ comprising dielectric layer 18 on first portion 20. Firstportion 20 and second portion 22 have different concentrations of B, andwhere higher comparative pressure produces greater concentration of B ineither portion 20 or 22. As with the above-described genericdescription, with the exception of pressure, preferably all parametersof all of the first and second conditions are substantially the samethroughout deposition of the first and second portions on the substrate.Preferably in this one example implementation, a change in depositionpressure occurs over a time interval of less than or equal to 5 seconds,and thereby produces deposited layer 18 to have the illustrated twodistinct portions 20 and 22 characterized by different substantiallyconstant concentrations of B. Again preferably, and by way of exampleonly, pressure control is preferably accomplished by manipulating avacuum pressure control device associated with the deposition chamber,for example the control devices illustrated in FIG. 1.

FIG. 3 illustrates an alternate embodiment wafer fragment 10 a. Likenumerals from the first described embodiment are utilized whereappropriate, with differences being indicated with the suffix “a” orwith different numerals. FIG. 3 depicts a high k ABO₃ comprisingdielectric layer 18 a formed by pressure changes occurring in multiplediscrete steps, thereby producing deposited layer 18 a to have threeportions 24, 26 and 28. Such portions are characterized by at least twodifferent substantially constant concentrations of B. For example,pressure during formation of regions 24 and 28 might be the same, withthe pressure during formation of region 26 being different. Alternatelyby way of example only, different substantially constant pressures mightbe utilized in formation of each of the three illustrated layers, andthereby producing three different substantially constant concentrationsof B in layer 18.

The invention also contemplates producing any of the above or otherconstructions in a manner whereby something other than discrete, shorttime interval pressure change occurs. In accordance with oneimplementation of the invention, during at least some of the feeding,pressure within the chamber is continuously varied effective to producea gradient in concentration of B across at least a some portion(preferably a majority portion) of the thickness of the deposited layer,and where higher comparative pressure produces greater concentration ofB in the deposited layer.

A construction produced from such an exemplary process is described withreference to FIG. 4 in connection with a substrate 10 b. Like numeralsfrom the first described embodiment are utilized where appropriate, withdifferences being indicated with the suffix “b” or with differentnumerals. Variable concentration of B in the illustrated layer 18 b isdepicted by the increasing density across an increasing gradient fromlow to high of the illustrated dots or peppering of the illustratedlayer 18 b. A continuously varying of pressure might be conducted toproduce a substantially constant concentration change of B per unitthickness across the portion of the thickness, as exemplified by theFIG. 5 graphical representation. Alternately by way of example only, acontinuously varying of pressure might be conducted to produce variableconcentration changes of B across the portion of the thickness where thecontinuous varying of pressure occurs. FIG. 6 illustrates such anexample where the concentration of B does not change along a straightline, and is thereby not a constant change across the thickness.

FIG. 4 also illustrates the entirety of the thickness of layer 18 bhaving been processed to produce variable B concentration throughout theentirety of the layer. Alternately, only a majority or some smallerportion might be produced to have a non-homogeneous construction.Further, and by way of example only, any of the example FIG. 2 and FIG.3 constructions might be processed to include some portion whichincludes a concentration gradient thereacross. Preferably in accordancewith this aspect of the invention, the pressure varying occurs over atime interval of at least 20 seconds, and thereby produces the depositedlayer to have at least one portion characterized by a gradient inconcentration of B thereacross.

The invention also has applicability in subatmospheric physical vapordeposition methods. FIG. 7 diagrammatically illustrates a physical vapordeposition system 50 utilizable in accordance with this aspect of theinvention. Like numerals from the first described embodiment areutilized where appropriate, with differences being indicated withdifferent numerals. A suitable sputtering target 54 comprising ABO₃ inaccordance with the above is positioned within a physical vapordeposition chamber 52. A wafer 56 is received over a wafer support 58within chamber 52. A suitable sputtering gas, preferably Ar, is fed tochamber 52 from a source 60 under conditions effective to sputter target54 and deposit a high k ABO₃ comprising dielectric layer over substrate56. During the feeding, pressure is varied within chamber 52 effectiveto produce different concentrations of B at different elevations in thedeposited layer and where higher comparative pressure produces greaterconcentration of B in the deposited layer, analogous to the firstdescribed embodiments. By way of example only, one sputtering systemincludes RF magnetron sputtering. Example preferred temperatures duringthe processing include wafer temperatures of from 400° C. to 650° C.Pressure is varied preferably between 1 mTorr and 300 mTorr. Bias powerto the target preferably ranges at from 1 to 5 W/cm² of target area.Exemplary RF power is from 10 to 200 watts. Sputtering gas can be eitherargon or a mixture of argon and oxygen, or any other appropriatesputtering gas. An exemplary flow rate for each of argon and oxygen in apreferred 1 to 1 ratio flow is from 100 sccm to 5000 sccm each.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A chemical vapor deposition method of forming a high k ABO₃comprising dielectric layer on a substrate, where “A” is selected fromthe group consisting of Group IIA and Group IVB metal elements andmixtures thereof, where “B” is selected from the group consisting ofGroup IVA elements and mixtures thereof, the method comprising: feedinga plurality of precursors comprising A, B and O to a chemical vapordeposition chamber having a substrate positioned therein underconditions effective to deposit a high k ABO₃ comprising dielectriclayer over the substrate; and during the feeding, varying pressurewithin the chamber effective to produce different concentrations of B atdifferent elevations in the deposited layer and where higher comparativepressure produces greater concentration of B in the deposited layer. 2.The method of claim 1 wherein A consists essentially of a mixture of Baand Sr.
 3. The method of claim 1 wherein B consists essentially of Ti.4. The method of claim 1 wherein A consists essentially of a mixture ofBa and Sr, and B consists essentially of Ti.
 5. The method of claim 1wherein flows of the precursors are maintained substantially constantwhile varying the pressure.
 6. The method of claim 1 wherein, with theexception of pressure, all of the conditions are maintainedsubstantially constant throughout deposition of the layer on thesubstrate.
 7. The method of claim 1 wherein the deposition is plasmaenhanced.
 8. The method of claim 1 wherein the deposition is not plasmaenhanced.
 9. The method of claim 1 wherein varying the pressure occursover a time interval of less than or equal to 5 seconds, and therebyproduces the deposited layer to have at least two distinct portionscharacterized by different substantially constant concentrations of B.10. The method of claim 1 wherein varying the pressure occurs over atime interval of at least 20 seconds, and thereby produces the depositedlayer to have at least one portion characterized by a gradient inconcentration of B.
 11. The method of claim 1 wherein the varying occursin multiple discrete steps thereby producing the deposited layer to haveat least three portions characterized by at least two differentsubstantially constant concentrations of B.
 12. The method of claim 1wherein the varying occurs in multiple discrete steps thereby producingthe deposited layer to have at least three portions characterized by atleast three different substantially constant concentrations of B. 13.The method of claim 1 wherein the deposition is subatmospheric.
 14. Achemical vapor deposition method of forming a high k ABO₃ comprisingdielectric layer on a substrate, where “A” is selected from the groupconsisting of Group IIA and Group IVB metal elements and mixturesthereof, where “B” is selected from the group consisting of Group IVAelements and mixtures thereof, the method comprising: feeding aplurality of precursors comprising A, B and O to a chemical vapordeposition chamber having a substrate positioned therein underconditions effective to deposit a high k ABO₃ comprising dielectriclayer over the substrate; and during at least some of the feeding,continuously varying pressure within the chamber effective to produce agradient in concentration of B across at least a majority portion of thethickness of the deposited layer and where higher comparative pressureproduces greater concentration of B in the deposited layer.
 15. Themethod of claim 14 comprising continuously varying pressure during amajority of the deposition of the layer on the substrate.
 16. The methodof claim 14 comprising continuously varying pressure throughoutdeposition of the layer on the substrate.
 17. The method of claim 14wherein the continuously varying of pressure is conducted to produce asubstantially constant concentration change of B per unit thicknessacross said portion of the thickness.
 18. The method of claim 14 whereinthe continuously varying of pressure is conducted to produce variableconcentration changes of B across said portion of the thickness.
 19. Themethod of claim 14 wherein flows of the precursors are maintainedsubstantially constant while varying the pressure.
 20. The method ofclaim 14 wherein, with the exception of pressure, all of the conditionsare maintained substantially constant throughout deposition of the layeron the substrate.
 21. The method of claim 14 wherein the deposition issubatmospheric, and the varying of pressure occurs by manipulating avacuum pressure control device associated with the chamber.
 22. Achemical vapor deposition method of forming a high k ABO₃ comprisingdielectric layer on a substrate, where “A” is selected from the groupconsisting of Group IIA and Group IVB metal elements and mixturesthereof, where “B” is selected from the group consisting of Group IVAelements and mixtures thereof, the method comprising: feeding aplurality of precursors comprising A, B and O to a chemical vapordeposition chamber having a substrate positioned therein under firstconditions effective to deposit a substantially homogenous first portionof a high k ABO₃ comprising dielectric layer over the substrate, thefirst conditions comprising a substantially constant first pressure; andwhile feeding the plurality of precursors, changing the first conditionsto second conditions that at least include a substantially constantsecond pressure which is different from the first pressure effective todeposit a substantially homogenous second portion of the high k ABO₃comprising dielectric layer on the first portion, the first and secondportions having different concentrations of B and where highercomparative pressure produces greater concentration of B.
 23. The methodof claim 22 wherein flows of the precursors are maintained substantiallyconstant during the first and second conditions.
 24. The method of claim22 wherein, with the exception of pressure, parameters of all of thefirst and second conditions are substantially the same throughoutdeposition of the first and second portions on the substrate.
 25. Themethod of claim 22 wherein A consists essentially of a mixture of Ba andSr.
 26. The method of claim 22 wherein B consists essentially of Ti. 27.The method of claim 22 wherein A consists essentially of a mixture of Baand Sr, and B consists essentially of Ti.
 28. The method of claim 22wherein the deposition is subatmospheric, and the varying of pressureoccurs by manipulating a vacuum pressure control device associated withthe chamber.
 29. A subatmospheric chemical vapor deposition method offorming a high k ABO₃ comprising dielectric layer on a substrate, where“A” is selected from the group consisting of Group IIA and Group IVBmetal elements and mixtures thereof, where “B” is selected from thegroup consisting of Group IVA elements and mixtures thereof, the methodcomprising: feeding a plurality of precursors comprising A, B and O to achemical vapor deposition chamber having a substrate positioned thereinunder conditions effective to deposit a high k ABO₃ comprisingdielectric layer over the substrate; and during the feeding,manipulating a vacuum pressure control device associated with thechamber to change deposition pressure within the chamber effective toproduce different concentrations of B at different elevations in thedeposited layer and where higher comparative pressure produces greaterconcentration of B in the deposited layer.
 30. The method of claim 29wherein the manipulating comprises changing a setting of a pressurecontrol valve proximate the chamber.
 31. The method of claim 29 whereinthe manipulating comprises changing speed of a vacuum pump.
 32. Themethod of claim 29 wherein the manipulating comprises changing ballastflow to a vacuum pump downstream of the chamber.
 33. The method of claim29 wherein flows of the precursors are maintained substantially constantthroughout deposition of the layer on the substrate.
 34. The method ofclaim 29 wherein, with the exception of pressure, all of the conditionsare maintained substantially constant throughout deposition of the layeron the substrate.
 35. The method of claim 29 wherein change indeposition pressure occurs over a time interval of less than or equal to5 seconds, and thereby produces the deposited layer to have at least twodistinct portions characterized by different substantially constantconcentrations of B.
 36. The method of claim 29 wherein change indeposition pressure occurs over a time interval of at least 20 seconds,and thereby produces the deposited layer to have at least one portioncharacterized by a gradient in concentration of B.
 37. The method ofclaim 29 comprising multiple discrete manipulatings thereby producingthe deposited layer to have at least three portions characterized by atleast two different substantially constant concentrations of B.
 38. Themethod of claim 29 comprising multiple discrete manipulatings therebyproducing the deposited layer to have at least three portionscharacterized by at least three different substantially constantconcentrations of B.